This invention relates to a pump which is suitable for pumping liquids such as water and oil from boreholes and the like. This pump operates by using relatively low gas pressure to elevate liquids from either shallow depths or relatively large depths.
Several different pumps are available to pump oil and water. The most widely used method for pumping oil is by using a jackpump connected to rods and tubings. Methods using air to propel liquids to the surface are air lift pumps, compressed air centrifugal pumps, and air pumps which require pressures sufficient to overcome the hydrostatic head of the liquid in the hole.
Jackpumps are relatively expensive, bulky, and because of the weight of the unit, a crane or hoist is necessary when the unit is installed and removed when servicing. Usually, these units are powered by electric motors, and the efficiency of lifting oil by this unit in the field is very low, usually less than one percent.
The air lift system is simple in use, but it depends on the relative densities of liquid and/or air-liquid mixture and for deeper wells, the required pressure and volume of air is quite large. Also, the air in this system often emulsifies the oil. A typical air lift system is described in U.S. Pat. No. 759,706. Anthony et al. U.S. Pat. No. 4,092,087 also discusses a very complicated air operated pump, where compressed gas or air in the range of 25-350 PSI is utilized with a large float to cause the pump to force the fluid up a tube. This complicated construction is obviously quite expensive.
Air pumps have been designed such that the liquid passes through a ball valve located on the bottom of the pump tank. U.S. Pat. No. 919,416 to Boulicault and Japanese Pat. No. 56-81299 by Nakayama discuss such a system with an air tube connected to the top of the tank and a liquid discharge tube extending to the bottom of the tank. After the tank fills with liquid flowing through the bottom ball valve, air pressure is applied to the air tube which closes the bottom valve and forces the contents of the liquid up the discharge tube. If the liquid level is several hundred feet or more above the pump, considerable air pressure is necessary to overcome the hydrostatic level of the liquid to close the bottom valve and even greater pressure is required to force the liquid to the surface. McLean et al U.S. Pat. No. 3,647,319 employs a similar method with the addition of a ball valve in the liquid discharge tube to prevent the liquid in the discharge line from returning to the tank of the pump. This unit requires rather large air pressure to elevate liquid from deeper wells. In column 3 of their patent, they state that full discharge will occur from any depth within range of 0 to 300 feet. At a depth of 1,000 feet below the top of the fluid, a pressure of about 460 PSI and a large air volume will be required to discharge water from that borehole.